The ventilation in the majority of old houses occurs through so-called natural draught, also known as natural ventilation, chimney effect or ascending convection current, which means that outside air will find its way in via leaks and/or via various types of air inlet devices, for example so-called spring valves in the walls of the building, often near windows, by which the air is progressively heated and gradually rises through various ducts, for example special exhaust air ducts, usually brought together in a ventilation chimney which discharges above the roof of the house.
The aforementioned incoming air can with advantage be supplied by means of an air inlet device in accordance with Swedish patent specification No. 7803220-8, which ensures an even flow. An inlet devices of this kind can with advantage also be utilized in conjunction with the present invention, where an even flow is of importance.
One disadvantage of the previously disclosed arrangements has been their sensitivity to the effect of the wind, which manifests itself in the fact that the outside air is able, under certain wind conditions which are dependent, amongst other things, upon the wind velocity, the wind temperature and the wind direction, to produce a self-ejecting underpressure and/or to penetrate the ventilation outlets as an overpressure and interfere with the flow of the out-flowing ventilation air. The outside air is also capable, under certain wind conditions, of entering via the aforementioned air inlet devices and of counteracting a gentle inward flow in this way.